<template>
  <div class="spec-preview">
    <img :src="nowImg.imgUrl"/>
    <!--    鼠标移动事件-->
    <div class="event" @mousemove="mousemoveHandler($event)"></div>
    <div class="big">
      <img :src="nowImg.imgUrl" ref="bigImg"/>
    </div>
    <!--    蒙板-->
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
export default {
  // eslint-disable-next-line vue/multi-word-component-names
  name: "Zoom",
  props: ['skuImageList'],
  data() {
    return {
      index: 0
    }
  },
  computed: {
    nowImg() {
      return this.skuImageList[this.index] || {} // 为例解决报错问题（因为一上来数据还没返回，skuImageList为undefined）
    }
  },
  mounted() {
    this.$bus.$on('getIndex', (index) => {
      this.index = index
    })
  },
  beforeDestroy() {
    this.$bus.$off('getIndex')
  },
  methods: {
    mousemoveHandler(event) {
      //处理蒙板
      let mask = this.$refs.mask
      let leftMargin = event.offsetX - mask.offsetWidth / 2
      let topMargin = event.offsetY - mask.offsetHeight / 2
      //还需约束范围
      if (leftMargin <= 0) {
        leftMargin = 0
      }
      if (leftMargin >= mask.offsetWidth) {
        leftMargin = mask.offsetWidth
      }
      if (topMargin <= 0) {
        topMargin = 0
      }
      if (topMargin >= mask.offsetHeight) {
        topMargin = mask.offsetHeight
      }

      mask.style.left = leftMargin + 'px'
      mask.style.top = topMargin + 'px'

      //处理大图
      let big = this.$refs.bigImg
      big.style.left = -2 * leftMargin + 'px'
      big.style.top = -2 * topMargin + 'px'
    }
  }
}
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>